Method, casting mold and device for producing a vehicle wheel

ABSTRACT

The invention relates to a method for producing a vehicle wheel from a light-metal material, in which the light-metal material is introduced in liquid form into a mold cavity of a casting mold. The vehicle wheel is produced by means of pressurized casting, wherein the casting mold is temperature-controlled in different regions to different temperatures.

The invention concerns a method for producing a vehicle wheel from alight-metal material, the light-metal material being introduced inliquid form into a mold cavity of a casting mold. Furthermore, theinvention relates to a casting mold for producing a vehicle wheel from alight-metal material, having mold parts forming a mold cavity forreceiving the light-metal material in liquid form, and an apparatus forproducing a vehicle wheel.

The basis for driving safety and driving comfort in light-metal wheelsfor passenger cars are the unsprung masses, the decisive factor beingthat the weight of the wheels is as low as possible. Due to the massinertia and the rotational torque, the aim is to use light-weightwheels. For this reason, on the one hand, attempts are being made toimplement light-weight wheel designs. On the other hand, efforts arebeing made to reduce weight by selecting materials. The current state ofthe art is cast or forged wheels made of aluminum or magnesium alloys, avery high percentage of which are produced using the low-pressure chillcasting or permanent mold casting process.

In addition to these driving dynamics requirements, aerodynamic orcrash-relevant wheel designs are playing an increasingly important role.Since the aerodynamic properties of the wheels are directly related tofuel consumption and CO₂ emissions, there was also a greater need foraction in the light of legislation. Due to homologation requirementswithin the overall approval process for passenger cars, in particularthe WVTA (Whole Vehicle Type Approval) in conjunction with the WLTP(Worldwide harmonized Light vehicles Test Procedure), these requirementshave become more stringent, so that the basic equipment of the completevehicle within the approval process (WVTA) no longer describes thevehicle, but all equipment variants. This change in the type testing bythe worldwide standardized light vehicle test procedure (WLTP) requiresa rethinking of the design of vehicle parts in terms of aerodynamics andlight-weight construction. In addition, these light-weight constructionand aerodynamic requirements are underpinned by the increasing use ofelectric mobility in line with the motto “Light-weight constructionincreases range”. Depending on the vehicle type, different wheeldimensions are used, which are aerodynamically worse and cause a higherblock function in frontal and offset crashes, which worsens theclassification result of the entire passenger car range.

These increasing demands, consisting of light-weight construction,aerodynamics and crash, require a change in the method for theproduction of vehicle wheels, since standard casting processes such aslow-pressure chill casting cannot optimally meet these requirements interms of process engineering.

In the cold-chamber casting process with conventional cold-chambercasting systems for the production of cast parts, these systems build upa clamping force by generating a lock through a clamping unit consistingof three machine plates, namely a machine shield, a movable clampingplate and a fixed clamping plate, four columns along which the movableclamping plate can be moved back and forth, and a drive unit for drivingthe movable clamping plate, usually via a hydraulically driven togglelever or double toggle lever. A casting mold is sampled with a movablemold half on the movable clamping plate and with a fixed mold half onthe fixed clamping plate. The necessary locking force is applied via theclamping unit by clamping the columns between the machine shield and thefixed clamping plate.

In conventional cold-chamber casting systems, the fixed clamping plateis followed in the axial direction by a casting unit by means of which amelt is fed to a mold cavity formed by the casting mold perpendicular tothe parting plane, i.e. perpendicular to the parting plane of the twomold halves, via a casting chamber through the fixed clamping plate andthe fixed mold half of the casting mold. For this purpose, the castingunit is equipped with a normally hydraulically driven casting plungerthat can be moved in the casting chamber.

An ejector unit is integrated in the clamping unit behind the movableclamping plate, which is normally also hydraulically driven to moveejector pins back and forth in the casting mold. The ejector pins arepassed through the movable clamping plate to scrape the cast parts fromthe moving half of the casting mold after opening the casting mold. Inaddition, a core pulling device is usually provided, which on themachine side consists of hydraulic cylinders, for example, which areusually mounted on the moving clamping plate, sometimes also on thefixed clamping plate.

As is well known, the casting process in cold-chamber casting plants isdivided into four successive phases, namely the dosing phase, thepre-filling phase, the mold-filling phase and the postpressing phase.

The dosing or metering can e.g. be carried out mechanically with a spoonor with compressed gas from a holding furnace via a channel or via ariser pipe, as in the so-called Vacural process. The dosing times aretypically between 3 s and 15 s, depending on the type and quantity ofdosing. If the dosing time is relatively long, there is a risk that partof the melt will already solidify in the casting chamber. Depending onthe machine design, the plunger speed in the pre-filling phase cantypically be adjusted in a range between 0.2 m/s and 0.6 m/s so that, onthe one hand, the melt is conveyed as quickly as possible and, on theother hand, air inclusions are avoided as far as possible, e.g. byoverturning of a wave of the melt building up in front of the plunger,by the formation of spray and/or by reflection in the casting residuearea.

In the pre-filling phase, the casting chamber is filled with melt andthe plunger conveys the melt up to the vicinity of the ingate.

To avoid cold flow points, the mold filling phase is as short aspossible; its duration is usually between 5 ms and 60 ms. In themold-filling phase, the plunger moves the melt at high speed, typicallyadjustable in a range of up to 10 m/s and more. At the end of themold-filling phase, high pressures occur by converting the kineticenergy into a pressure pulse, so that there is a risk of the moldtearing. Modern casting machines therefore have means to absorb thekinetic energy towards the end of the filling phase.

In the post-pressing phase or holding-pressure phase of a cold chambercasting machine, a holding pressure of 300 bar to 1500 bar, and in somecases even more, is usually set via a multiplier. The melt solidifiesunder the holding pressure and air trapped during mold filling iscompressed under the static holding pressure. The proportion of airtrapped under the holding pressure in the volumetric porosity is low.The volumetric porosity usually consists of blowholes, the cause ofwhich is insufficient replenishment of a shrinkage-related portion ofthe melt at the transition from liquid to solid.

In conventional cold-chamber casting systems, the ingates are generallythin-walled in relation to the wall thickness of the cast parts, whichmeans that the melt is still liquid in some areas of the cast part,while it has already partially or completely solidified in the ingatearea, which makes further feeding impossible or at least difficult. Theformation of a solidified rim shell in the casting chamber after dosingor metering leads to the fact that part of the melt is neither availablefor filling the casting mold nor for feeding the shrinkage-relatedportion in the mold cavity. Pressing residual melt out of the castingresidue area for replenishment requires a high holding pressure.

The high pressures at the end of the mold-filling phase and in theholding-pressure phase require high holding forces of the casting mold,which must be applied via the clamping unit of the casting machine.

High casting forces lead to elastic deformation of the casting mold andpossibly to a bulge around the mold cavity, which can cause burrformation around the cast part in the parting plane as well as in theareas of slides and slide guides.

The high pressures require a relatively large thickness of the fixedclamping plate and consequently a correspondingly long casting chamber,which in turn limits the filling level in the casting chamber totypically 15% to a maximum of about 70%, with a correspondingly largeair volume in the casting chamber. The conventional orientation of thecasting unit relative to the clamping unit results in relatively longflow paths of the melt in the casting chamber and in the casting systemand often a cranking of the casting system or the anvil. The applicationof high pressures can also lead to elastic deformation of the solidifiedcasting residue and the casting chamber in the casting residue area andthus to jamming of the casting residue in the casting chamber, so thatunder certain circumstances high opening forces are required to tear thecasting residue out of the casting chamber. This can lead to a highand/or premature wear of the casting chamber and the plunger. Inaddition, jamming of the casting residue in the casting chamber oftenresults in the application of an excessive amount of piston lubricant,which can lead to inclusions in the cast part.

With horizontally arranged casting chambers, these are heated more inthe lower area than in the upper area during filling by the hot melt, sothat the thermal load causes a deformation of the casting chamber, whichcauses friction between the casting chamber and the casting piston,which must follow the course of the casting chamber in the pre-fillingphase and the mold-filling phase. The conventional orientation of thecasting chamber relative to the mold or barrel causes a verticaldeflection of the melt at the transition from the casting chamber to themold or barrel in the parting plane, which is problematic in terms offlow mechanics and also thermally problematic. Any deflection of themelt leads to turbulence during mold filling, to a higher energyrequirement in the casting drive and to the risk of noticeable airinclusions and erosion in the area of the casting set and the castingmold.

The described system-related disadvantages of conventional cold chambercasting systems worsen the casting result and require a very stable andcost-intensive machine design. In addition, due to the overall design ofconventional casting machines, the clamping of the casting mold is atime-consuming and cost-intensive process.

It is therefore an object of the present invention to create a methodand a casting mold for producing a vehicle wheel from a light-metalmaterial which are capable of meeting these constantly increasingrequirements in terms of light-weight construction, aerodynamics andcrash behavior of the vehicle wheel.

According to the invention, this object is met by the features mentionedin claim 1.

In addition to the low machine and tool requirements, the method inaccordance with the invention offers the best prerequisites for meetingthe above-mentioned increased requirements with the methods and systemsknown from the state of the art. By using pressurized casting instead ofthe previously used low-pressure chill casting for vehicle wheels withits limited possibilities or the conventional cold-chamber castingprocess for other cast parts with its current process-relateddisadvantages, it is possible to carry out various light-weightconstruction optimizations, aerodynamic optimizations and crashoptimizations as well as system-related mold designs as light-weightconstruction and process optimization.

A method change from low-pressure chill casting with its limitedpossibilities with regard to casting cross-section, quality of thecasting result due to high tool temperatures of over 500° C., topressurized casting thus enables, in addition to various optimizationswith regard to light-weight construction, aerodynamics and crashbehavior, also system-related form designs as lightweight constructionand process optimizations.

The temperature control of the casting mold according to the inventionleads to a very fast and complete filling of the mold cavity, wherebysegregation of the liquid light-metal material is avoided. The solutionaccording to the invention enables a desired temperature level withinthe mold cavity, so that, in addition to the uneven heating of thecasting mold, the associated deformation of the casting chamber isavoided and thus the premature solidification of the molten light-metalmaterial is prevented in certain areas. In addition to increasing theservice life of the pistons and the casting mold, this also reduces thepiston forces.

By using pressurized casting and tempering the casting mold in differentareas to different temperatures, very low forces occur during thecasting process, resulting in low-turbulence or turbulence-free castingof the vehicle wheel. Although the advantages of the cold-chambercasting process are used for the production of light-metal wheels, theproblems otherwise resulting from this process are avoided.

Furthermore, the method according to the invention allows very smallwall thicknesses of up to 1 mm in certain areas of the vehicle wheel andin certain cases even less. The possible reduction of wall thicknessesmakes it possible to design a vehicle wheel that has significantlybetter properties than known vehicle wheels with regard to crashbehavior. In particular, the vehicle wheel produced with the methodaccording to the invention can be optimized for a desired crashbehavior.

Due to such thin wall thicknesses, the visible side of the vehicle wheelcan be designed to be almost completely closed without significantlyincreasing the weight of the vehicle wheel. This can significantlyimprove the aerodynamics of the vehicle wheel. Of course, openings, forexample for ventilating a vehicle brake, can also be integrated intosuch a visible side. A structure increasing the strength of the vehiclewheel can be located within such a disc-like design of the visible side.This means that, compared to known solutions, significant improvementscan also be achieved in the aerodynamics of the vehicle wheelmanufactured using the method in accordance with the invention.

A further advantage resulting from the use of the method is the lowdraft angle of up to 1 degree or less, which opens up previously unknownstylistic design possibilities for the vehicle wheel. Furthermore, veryfine surfaces with a very small radius of 1 mm or less can be created.

The fact that the vehicle wheel can be finished in one casting reducesthe machining required after casting by approximately 80% or more. Thereduced post-processing requirements mean that less waste is produced,which helps to protect the environment. The method, which is inaccordance with the invention, considerably reduces the casting time andenables a virtually burr-free casting, while also requiring less rawmaterial and energy. Furthermore, the rapid casting and solidificationwith casting skin means that otherwise necessary artificial ageing canbe completely or partially eliminated. The vehicle wheel produced withthe method according to the invention has a low distortion, which alsoallows the fine gradations required for bright turning.

The light-weight construction achievable with the method according tothe invention increases the range of motor vehicles equipped with suchvehicle wheels, which contributes to a reduction of the burden on theenvironment.

If, in a very advantageous further development of the invention, inareas, in which the vehicle wheel has a small cross-section, the castingmold is tempered to high temperatures, and in areas, in which thevehicle wheel has a large cross-section, the casting mold is tempered tolow temperatures, it is ensured that the melt remains liquid for asufficiently long time in relatively narrow areas of the mold cavity toprevent premature solidification of the same and that in relatively wideareas of the mold cavity solidification begins in good time. Overall,this results in uniform solidification of the entire vehicle wheel to becast.

With regard to rapid filling of the mold cavity and the associateduniform solidification of the liquid light-metal material, it has provedto be particularly advantageous if the molten light-metal material isintroduced into the mold cavity at a high speed of more than 5 m/s.

It may also be provided that a venting area, in which the casting moldis vented, is tempered to a much lower temperature than the other areasof the casting mold. This ensures rapid solidification of the melt inthe venting area, which prevents the melt from escaping from the castingmold. In addition, this also allows the liquid light-metal material tosolidify in a compact design, despite venting, even at high castingspeeds.

A casting mold for producing a vehicle wheel according to the inventionis specified in claim 5.

The casting mold according to the invention enables a very simpleadjustment of different temperature ranges within the casting moldthrough the use of the tempering devices, so that the vehicle wheel tobe cast can be produced under the optimum conditions in each case. Thecasting mold according to the invention can have a relatively simpledesign and is always kept at the set temperatures by the temperingdevices.

With regard to the setting of the desired temperatures at the transitionof the casting mold into the mold cavity, it is particularlyadvantageous if the tempering devices are formed as pressurized watercircuits, electric heating cartridges and/or pressurized oil circuits.

If the mold parts and/or inserts connected to the mold parts and/orventing elements consist of different materials, the heat outflow and/orheat inflow can be controlled relatively easily.

Furthermore, it may be provided that the tempering devices are inoperative connection with a control device for controlling and/orregulating the temperatures of the tempered areas. In this way, thetemperatures of the individual areas of the mold cavity or casting moldcan be controlled or regulated very easily.

With regard to a simple construction or design of the casting moldaccording to the invention, an advantageous further embodiment canconsist in the fact that at least two mold parts movable relative toeach other are provided.

A further advantageous embodiment of the invention may consist in thefact that at least one of the mold parts has a plurality of tuningelements for adjusting the mold part to different temperatures acting onthe casting mold. By means of these tuning elements at least one of themold parts and thus the entire casting mold can be very well tuned toeach other with respect to the matching of the individual components,since the tuning elements are suitable for compensating tolerancesbetween the individual components of the casting mold. It also allowsthe casting mold to be used at temperatures other than those for whichit was designed, thus significantly reducing costs. The tuning elementscan also be made of different materials and can compensate for thedifferent sizes of the components involved depending on the productionof the molded part and the heat input of the molded part. In addition tothe size compensation, the tuning elements can either insulate the heator transfer the heat in a targeted manner, so that in addition to themolding production and the molding heat input, the different sizes arecompensated and an insulating effect is achieved or heat is transferred.In addition to size compensation, the tuning elements are also capableof absorbing and/or damping the shocks and/or forces introduced.

In order to prevent the melt from escaping through the venting of thecasting mold, it can also be provided that in a venting region of themold cavity of the casting mold a surface change in the form of atempered labyrinth-like structure and/or at least one change incross-section and/or at least one deflection is provided.

An apparatus for producing a vehicle wheel with such a casting mold isgiven in claim 12.

The apparatus, which may be in the form of a casting machine, forexample, can be used particularly advantageously for carrying out themethod according to the invention.

In order to achieve a simple and safe opening and closing of the castingmold, it can be provided that at least one of the mold parts of thecasting mold is movable in the closing direction of the casting moldrelative to another mold part by means of at least one guide element notbelonging to the casting mold. In this way it is also possible to avoidadditional guides within the casting mold and to move the mold parts ofthe casting mold without such guides. By arranging the guide elementsinside the apparatus and especially not inside the casting mold, theguide elements can be used for the most different casting molds, so thatconsiderable cost savings can be achieved. In addition, in this wayquick casting mold changes, i.e. quick changes of the mold parts of thecasting mold, are possible.

Another advantageous embodiment of the invention may be that the moldparts are thermally separated from guide elements moving the same. Thisprevents excessive heating of the guide elements so that they cannotwarp and a high degree of accuracy in the movement of the components ofthe apparatus is achieved and disturbances are avoided.

Another advantageous embodiment of the apparatus can be that at leasttwo of the mold parts are movable by means of respective grippingelements in a direction perpendicular to the closing direction. Thisallows a very fast opening and closing of the casting mold, which canconsiderably increase the productivity of the apparatus according to theinvention.

A simple and quick connection of the mold parts with the guide and/orgripping elements results when at least one of the mold parts can beconnected to the at least one guide element and/or to the grippingelements by means of quick-connection means.

In order to be able to supply and/or operate the tempering devices in aneffective manner, it can also be provided that respective units forsupplying the tempering devices are integrated into the apparatus.

A further advantageous embodiment of the invention may be that at leastone vacuum unit is provided for extracting air from the mold cavity.This vacuum unit enables the air to be sucked out of the mold cavityquickly and easily in order to fill it with the liquid light-metalmaterial.

In the following, examples of the embodiments of the invention are shownin principle on the basis of the drawings.

In the drawings:

FIG. 1 is a side view of an apparatus according to the invention in afirst state;

FIG. 2 is a view according to arrow II of FIG. 1;

FIG. 3 is a perspective view of the apparatus of FIG. 1;

FIG. 4 is a side view of the apparatus of FIG. 1 in a second state;

FIG. 5 is a perspective view of the apparatus of FIG. 4;

FIG. 6 is a side view of the apparatus of FIG. 1 in a third state;

FIG. 7 is a perspective view of the apparatus of FIG. 6;

FIG. 8 is a side view of the apparatus of FIG. 1 in a fourth state;

FIG. 9 is a perspective view of the apparatus of FIG. 8;

FIG. 10 is a casting mold according to the invention;

FIG. 11 is a further view of a part of the casting mold according to theinvention; and

FIG. 12 is another view of a part of the casting mold according to theinvention.

FIGS. 1 to 9 show different views of an apparatus 1 for producing avehicle wheel 2 shown in FIGS. 6 to 9 by means of pressurized casting.The vehicle wheel 2 can basically be of any size and shape. The vehiclewheel 2 shown in FIGS. 6 to 9 is therefore to be regarded as purelyexemplary. A light-metal material is used for the pressurized casting ofthe vehicle wheel 2, preferably an aluminum or magnesium material. Forthis purpose, light-metal materials known per se and suitable for themethod described below can be used for the production of the vehiclewheel 2.

The apparatus 1 has a casting mold 3, which in the representation ofFIGS. 1, 2 and 3 is in a closed position. In the present case, thecasting mold 3 has four mold parts, namely a rigid or immobile mold half4, a movable mold half 5, an upper gate or slide 6 and a lower gate orslide 7. The mold parts of the casting mold 3 can be accommodated withor without a zero point system and they can have a very smooth andhigh-quality surface which does not need to be treated with a coating orthe like, or only to a very limited extent, resulting in a very highsurface quality of the vehicle wheel 2. Of course, the casting mold 3can also have more than the four mold parts described and illustratedhere. The movable mold parts, i.e. the movable mold half 5, the upperslide 6 and the lower slide 7, can be brought from the state shown inFIGS. 1, 2 and 3 to the states according to FIGS. 4 and 5, 6 and 7 aswell as 8 and 9 by means of the respective guide elements describedbelow. All of these guide elements described below are part of theapparatus 1 and do not belong to the casting mold 3.

For guiding the movement of the movable mold half 5 in the closingdirection of the casting mold 3, marked with the arrow “x” in FIG. 1,and against this closing direction x, several horizontally running guidecolumns 8 are used, which are mounted on one side on a movable clampingplate 9 and on the other side on a rear machine shield 10, which forms acounter bearing. By moving the movable clamping plate 9, which is also aguide element for the casting mold 3, against the closing direction x,the movable mold half 5 is brought from its position shown in FIG. 1 tothe position shown in FIG. 4. When the movable mold half 5 is movedrelative to the rigid mold half 4, the upper slide 6 and the lower slide7 are also moved against the closing direction x relative to the rigidmold half 4. Drive devices known per se and not shown herein can be usedto drive the movable clamping plate 9, which in this case is movablymounted on rails 11 of apparatus 1. The guide columns 8 form a guide forthe movable clamping plate 9 and absorb the horizontal clamping forcesduring casting. The rigid mold half 4 is attached to a fixed clampingplate 12 which is connected to a casting unit 13 which serves tointroduce the liquid light-metal material into a mold cavity 14 formedbetween the mold parts of the casting mold 3, which in a manner knownper se comprises the negative mold of the vehicle wheel 2 to beproduced. The filling of the mold cavity 14 with the liquid light-metalmaterial takes place in particular from the outer circumference of themold cavity 14. The casting mold 3 is preferably designed in such a waythat spraying of the material is avoided when the liquid light-metalmaterial is introduced into the mold cavity 14. The liquid light-metalmaterial is introduced into the mold cavity 14 at a relatively lowpressure of up to 100 bar or slightly more.

During the actual casting process, the movable clamping plate 9 and thefixed clamping plate 12, on which the movable clamping plate 9 issupported, also generate the clamping force. For this purpose, the driveelements or devices used to move the movable clamping plate 9 can havehydraulic cylinders and/or toggle lever elements or mold closingelements, for example. The casting mold 3 can be clamped by means ofmanual, semi-automatic or fully automatic clamping elements via form fitand/or frictional connection. The fixed clamping plate 12 can have amold spraying device not shown and/or an integrated pressure mediumsystem.

The upper slide 6 can be moved from its position shown in FIG. 1 or FIG.4 to the position shown in FIG. 6, in which the upper slide 6 has beenmoved vertically upwards relative to the movable mold half 5, by meansof an upper gripping element 15. In a similar way the lower slide 7 canalso be moved downwards by means of a lower gripping element 16 from itsposition shown in FIGS. 1 and 4 to its position shown in FIG. 6 relativeto the movable mold half 5. The gripping elements 15 and 16 as well asthe movable clamping plate 9 can be operated manually,semi-automatically or fully automatically. The two gripping elements 15and 16 also represent guide elements for the casting mold 3. The guideelements for moving the mold parts of the casting mold 3 can also beequipped with a pressure medium in a way not shown.

While in the present case the upper slide 6 and the lower slide 7 aremoved in the vertical direction, it would also be possible to separatethe casting mold 3 in the area of the two slides 6 and 7 in the verticaldirection and thus move the two slides in the horizontal direction. Thetwo gripping elements 15 and 16 would be left and right grippingelements in this case. Preferably, the two slides 6 and 7 are moved bymeans of the respective gripping elements 15 and 16 in a directionperpendicular to the closing direction x.

In the method for the production of the vehicle wheel 2 carried out withthe apparatus 1 and the casting mold 3, the light-metal material is thusintroduced in liquid form into the mold cavity 14 of the casting mold 3by means of the casting unit 13. This introduction of the liquidlight-metal material takes place at a high speed of more than 5 m/s.This high speed is achieved by a corresponding movement of a piston ofthe casting unit 13 not shown. The vehicle wheel 2 is produced by meansof pressurized casting, whereby the casting mold 3 is tempered todifferent temperatures in different areas. This different tempering ofcasting mold 3 will be described in more detail at a later date using anexample. Preferably, in areas in which the vehicle wheel 2 has a smallcross-section, the casting mold 3 is tempered to high temperatures andin areas, in which the vehicle wheel 2 has a large cross-section, thecasting mold 3 is tempered to low temperatures. The temperature controlof the casting mold 3 allows the solidification behavior of the liquidlight-metal material to be controlled or adjusted, although the vehiclewheel 2 has very different cross-sections. In addition, an area, inwhich the casting mold 3 is vented, is tempered to a much lowertemperature than the other areas of the casting mold 3. This area, inwhich the casting mold 3 is vented, will also be described in moredetail later.

The mold parts of the casting mold 3, i.e. the rigid mold half 4, themovable mold half 5, the upper slide 6 and the lower slide 7, canconsist entirely or partially of different materials. In particular, thematerials of the individual mold parts can be selected depending on thetemperatures to be set when the casting mold 3 is tempered.

After the liquid light-metal material has solidified, the mold parts aremoved apart in the manner described above to open the casting mold 3.Ejection of the cast part produced by the method, i.e. the vehicle wheel2, is carried out by means of an ejector unit 17 which, like the guidecolumns 8, is mounted on the one hand on the movable clamping plate 9and on the other hand on the rear machine shield 10. In the presentcase, the ejector unit 17 has a hydraulic unit 18, which ensures themovement of the ejector unit 17 in a manner known per se. After ejectionof the vehicle wheel 2 from the casting mold 3, the casting mold 3 can,in the opposite direction, i.e. from the state according to FIGS. 8 and9 over the state according to FIGS. 6 and 7, the state according toFIGS. 4 and 5 be brought to the state according to FIGS. 1, 2 and 3, inorder to produce the next vehicle wheel 2 by introducing the liquidlight-metal material into the mold cavity 14.

After completion, the represented vehicle wheel 2 can of course beconnected to a tire not shown in the drawings to be filled with air orgas. The vehicle wheel 2 can also consist of several individual parts,which can also be produced using the method described herein.

FIGS. 10, 11 and 12 show an exemplary embodiment of the casting mold 3,showing the rigid mold half 4, the movable mold half 5, the upper slide6 and the lower slide 7. The upper gripping element 15 and the lowergripping element 16 can also be seen in these figures. FIG. 10 alsoshows that the upper slide 6 and the lower slide 7 are connected to theupper gripping element 15 and the lower gripping element 16 respectivelyby means of quick-connection means 19 and 20, by means of which it ispossible to quickly connect the guide elements belonging to theapparatus 1 with the mold parts belonging to the casting mold 3 in orderto ensure quick opening and closing of the casting mold 3 by moving themold parts relative to each other as described above.

In addition, FIG. 10 shows that the upper slide 6, the lower slide 7 andthe movable mold half 5 are thermally separated from the correspondingguide elements, i.e. the upper gripping element 15, the lower grippingelement 16 and the movable clamping plate 9. Corresponding insulatingelements 21 are provided for this purpose, not all of which are visibledue to the course of the sectional view and which may also be providedbetween the rigid mold half 4 and the fixed clamping plate 12. Thisthermal separation of the mold parts from the guide elements preventsunintentional heating of the guide elements, so that the function of theapparatus 1 with regard to the opening and closing of the casting mold 3is guaranteed even in the event of temperature changes.

FIG. 10 also shows several tempering devices by means of which thecasting mold 3 can be tempered to different temperatures in order toenable uniform solidification of the light-metal material within themold cavity 14. The tempering devices are preferably pressurized watercircuits, of which several holes 22 are shown in FIG. 10, electricheating cartridges 23 and pressurized oil circuits, of which severalholes 24 are also shown in FIG. 10. If necessary, other heating orcooling elements can also be used as tempering devices.

The tempering devices, i.e. the pressurized water circuits, the electriccartridge heaters 23 and/or the pressurized oil circuits are connectedto a control device 25, also shown in FIG. 10, so that the temperaturesof the areas temperature controlled by the tempering devices can becontrolled and/or regulated. The control device 25 can also be inoperative connection with temperature sensors not shown, which measurethe actual temperature of the individual parts of the casting mold 3 andthus enable the temperature to be set correctly. The control device 25is also capable of monitoring the temperatures of the molded part or ofthe molding zones in addition to other process data and/or geographicaldata and/or other monitoring information and transmitting them to ahigher-level system, for example a machine control system. In this way,the casting mold 3 can be specifically tempered during production and/orfor preheating, whereby all influencing parameters, such as differentthermal expansions of the components involved, can be monitored andcontrolled based on the different temperatures and thermal expansioncoefficients of the mold parts.

The temperature control of the casting mold 3 can of course be designeddifferently for each individual mold and thus for each individualvehicle wheel 2 to be produced with the casting mold 3 or the apparatus1.

FIGS. 1, 4, 6 and 8 show very schematically units 26, which are used tosupply the temperature control units for the temperature control of thecasting mold 3 and which are integrated in the apparatus 1. In thepresent case, the units 26 are shown as being integrated in the rails11. However, the units 26 can of course also be located or attached atother positions within the apparatus 1.

Furthermore, FIGS. 1, 4, 6 and 8 show a vacuum unit 27, which is used toextract air from mold cavity 14. The vacuum unit 27, by means of which acorresponding vacuum is generated, is also integrated in the apparatus 1and again shown purely as an example in the rails 11. The connection ofthe units 26 with the tempering devices and the connection of the vacuumunit 27 with the mold cavity 14 are not shown in the figures; they canbe carried out in the most varied and familiar ways.

FIG. 11 shows a perspective view of a part of the casting mold 3, inwhich the upper slide 6, the lower slide 7, the movable mold half 5, thecontrol device 25 and a part of the mold cavity 14 can be seen. The twogripping elements 15 and 16 as well as their connection to the twoslides 6 and 7 can also be clearly seen in FIG. 11. Furthermore, itresults from FIG. 11 that at least one of the moldings, in the presentcase both the upper slide 6 and the lower slide 7, has several tuningelements 28 by means of which the moldings can be matched or tuned toeach other. In the present case, the two slides 6 and 7 are matched tothe rigid mold half 4 not shown in FIG. 11 by means of the tuningelements 28. In this way, tolerance deviations that inevitably occurduring the manufacture of the individual mold parts can be compensated.Furthermore, the tuning elements 28 serve to adjust the mold parts ofthe casting mold 3 to different temperatures acting on the casting mold3. The tuning elements 28, which can also be denominated as insertparts, can be made of a different material than the slides 6 or 7 in oron which they are arranged.

By means of the tuning elements 28, which have the most variedthicknesses and can also be designed as tuning cylinders if necessary,it is possible to tune the casting mold 3 in separating areas betweenthe mold parts of the casting mold 3 in such a way that all mold partsof the mold remain closed even under bursting pressure in order toprevent the liquid light-metal material from escaping. In this way, themold parts of the casting mold 3 with their temperature zones can beadjusted in such a way that, in addition to the technological andeconomic requirements that inevitably arise with vehicle wheels 2, thetechnological and economic design of the casting mold 3 in conjunctionwith the problems that arise with conventional molds is also taken intoaccount in the production of vehicle wheels 2. The tuning elements 28can also be reworked or exchanged after appropriate testing, so that asecure sealing of the casting mold 3 is guaranteed.

FIG. 12 shows a view of another mold part of the casting mold 3, namelythe rigid mold half 4, which has a venting area 29 adjoining the moldcavity 14, through which the air inside the mold cavity 14 at the startof the casting process can escape. To prevent the liquid light-metalmaterial from escaping from the venting area 29 in addition to the air,the venting area is, as already mentioned, tempered to a much lowertemperature than the other areas of the casting mold 3. In addition, atemperature-controlled or tempered, labyrinth-like structure 30 isprovided in the venting area 29, which makes it more difficult for theliquid light-metal material to escape from the mold cavity 14. Inaddition or as an alternative to the labyrinth-like structure 30, theventing area 29 may also have cross-sectional changes, surfaceenlargements or surface reductions and/or deflections. The venting area29 or a venting element forming the venting area 29 can be made of adifferent material than the other components of the casting mold 3. Forexample, copper materials such as brass or bronze can be used for theventing area 29. Of course, the same or similar venting areas as theventing area 29 can also be located at other points in the mold cavity14.

The venting area 29, which can also be denominated as a venting unit,enables a system that brakes the liquid light-metal material in itselfthrough its own heat management in conjunction with the geometric designdescribed, so that, depending on the requirements, a connection to thevacuum unit 27 can be controlled selectively with full cross-section orreduced cross-section via one or more holes 31 in order to be able torealize short venting distances. In some cases, these venting areas 29can also be provided with a vacuum valve connection or can also be usedwithout a subsequent vacuum connection in order to serve as a completeor partial overflow for the casting mold 3.

FIG. 12 also shows a closed belt or ring 32, which is formed byoffsetting the planes of the rigid mold half 4. In the closed state ofthe casting mold 3 the tuning elements 28 rest against the ring 32 inorder to guarantee the tightness of the casting mold 3. The ring 32 thusabsorbs the forces occurring during casting.

What is claimed is:
 1. A method of producing a vehicle wheel from alight-metal material comprising introducing a light-metal material inliquid form into a mold cavity of a casting mold, wherein the vehiclewheel is produced using pressurized casting, and wherein the castingmold is tempered to different temperatures in different areas.
 2. Themethod of claim 1, wherein in areas in which the vehicle wheel (2) has asmall cross-section, the casting mold is tempered to high temperatures,and in areas in which the vehicle wheel has a large cross-section, thecasting mold is tempered to low temperatures.
 3. The method of claim 1,wherein the molten light-metal material is in a molten state and isintroduced into the mold cavity at a speed of more than 5 m/s.
 4. Themethod of claim 1, wherein a venting area, in which the casting mold isvented, is tempered to a much lower temperature than the other areas ofthe casting mold.
 5. A casting mold for producing a vehicle wheel from alight-metal material comprising mold parts that form a mold cavity forreceiving the light-metal material in liquid form, wherein the castingmold has areas tempered to different temperatures using temperingdevices.
 6. The casting mold of claim 5, wherein the tempering devicesare formed as pressurized water circuits, electric heating cartridges,and/or pressurized oil circuits.
 7. The casting mold of claim 5, whereinthe mold parts and/or inserts connected to the mold parts and/or ventingelements comprise different materials.
 8. The casting mold of claim 5,wherein the tempering devices are in operative connection with a controldevice for controlling and/or regulating the temperatures of thetempered areas.
 9. The casting mold of claim 5, wherein at least twomold parts movable relative to each other are provided.
 10. The castingmold of claim 5, wherein at least one of the mold parts has a pluralityof tuning elements for adjusting the mold part to different temperaturesacting on the casting mold.
 11. The casting mold of claim 5, wherein ina venting area of the mold cavity of the casting mold a surface changein the form of a tempered labyrinth-like structure and/or at least onechange in cross-section and/or at least one deflection is provided. 12.An apparatus for producing a vehicle wheel comprising the casting moldof claim
 5. 13. The apparatus of claim 12, wherein at least one of themold parts of the casting mold is movable in the closing direction ofthe casting mold relative to another mold part by means of at least oneguide element not belonging to the casting mold.
 14. The apparatus ofclaim 12, wherein the mold parts are thermally separated from guideelements moving the same.
 15. The apparatus of claim 12, wherein atleast two of the mold parts are movable by means of respective grippingelements in a direction perpendicular to the closing direction.
 16. Theapparatus of claim 13, wherein at least one of the mold parts can beconnected to the at least one guide element and/or to the grippingelements by means of quick-connection means.
 17. The apparatus of claim12, wherein respective units for supplying the tempering devices areintegrated into the apparatus.
 18. The apparatus of claim 12, wherein atleast one vacuum unit is provided for extracting air from the moldcavity.